public class 面积 {
    private double a;
    private double b;
    private double r;

    public void RectangleArea(double a, double b) {
        this.a = a;
        this.b = b;
        System.out.println("长方形的面积：" + a * b);
    }

    public void RoundArea(double r) {
        this.r = r;
        System.out.println("圆的面积：" + Math.PI * r * r);

    }
}

class TestArea {
    public static void main(String[] args) {
        面积 面积 = new 面积();
        面积.RectangleArea(2, 4);
        面积.RoundArea(2);
    }
}